The present invention relates to an apparatus for die casting an internal passageway. In particular, the present invention relates to an apparatus for die casting an object having an internal passageway extending transversely to the line of draw of the mold and an object manufactured with such apparatus.
Oil pans for automotive engines are commonly manufactured as an aluminum die cast. The die casting process is preferred over other casting methods, such as sand or investment casting, because die casting generally has a higher production rate and the process can be more automated.
Four wheel drive vehicles such as sport utilities and pick up trucks have become increasingly popular. With the increasing demand for these vehicles, there has been a desire on the part of the vehicle manufacturers to increase power and functionality of the vehicles without significantly increasing the size of the engine and the vehicle. As a result, engine designers have specified that the transmission axle is to extend through the oil pan without affecting the oil capacity of the pan, thereby requiring an internal passageway.
An undercut structure which extends transverse to the line of draw of the mold cannot be made using conventional die casting techniques. The undercut makes it impossible for the cast object to be removed from conventional molds. As a result, undercut structures are generally cast using sand casting techniques wherein the mold core which forms the undercut is broken away after the cast object has been removed from the mold. Such a technique is described in U.S. Pat. No. 4,961,458.
The additional steps of forming a sand cast and removing the sand cast increases cycle time increases the need for manual labor and, ultimately, the cost of the finished cast product.
According to the present invention, there is a provided a die casting apparatus which addressed the disadvantages of the prior art die casting molds.
The die casting apparatus, according to the present invention, comprises a pair of mold assemblies which include molding surfaces cooperating to define a first mold cavity therebetween for casting a first portion of a cast object therein. One of the mold assemblies comprises a fixed mold core, and a movable mold core movable with respect to the fixed mold core along a core axis between a closed position and an open position. The mold cores include casting surfaces disposed such that in the closed position the casting surfaces cooperate to define a second mold cavity therebetween extending transversely to the core axis and in communication with the first mold cavity for casting a remaining portion of the object integral with the first portion, while in the released position the object is substantially released from the one mold assembly.
In a preferred embodiment of the invention, the mold assemblies are movable with respect to each other, along a mold axis, between an open mold position and a closed mold position. The mold assemblies comprise a male mold assembly and a female mold assembly for receiving the male mold assembly therein, with the first mold cavity defined therebetween being shaped for casting a side wall and a base integrally cast with the side wall. The second mold cavity is shaped for casting a tubular passageway integrally cast with the side wall. Preferably, the die casting apparatus also includes a transversely-movable core which is movable within the second mold cavity for casting the tubular passageway between the casting surfaces and the transversely-movable core.
The male mold assembly includes the fixed mold core and the movable mold core. The movable mold core moves relative to the fixed mold core between the closed casting position and the open removal position. The molding surface of the movable mold core is positioned at the end of the movable mold core and is oriented such that when the movable mold core is in the casting position, the molding surface of the movable mold core coincides with the molding surface of the fixed mold core. In addition, the movable core casting surface is positioned a distance from the end of the movable core molding surface.
Once the object has been cast, the male mold assembly and the female mold assembly open and move to the open mold position, and the transversely-movable core is withdrawn from the second mold cavity. The movable mold core casting surface then moves relative to the fixed mold core casting surface urging the tubular passageway away from the fixed mold core casting surface while also urging the side wall and base away from the fixed core molding surface. Once in the removal position, the cast object is dislodged from the movable core by moving the cast object transversely with respect to the mold cores. The movable core is then returned to the casting position and the cycle is repeated.